Field of the Invention
The present invention relates to an electrophotographic image forming apparatus. More specifically, the present invention relates to an electrophotographic image forming apparatus that can prevent the occurrence of image deletion, raindrop-like spots, and slipping-through of toner and can maintain cleanability for the long term.
Description of the Related Art
In an electrophotographic image forming apparatus, the surface of a charged organic photoreceptor (hereinafter, also referred to as “photoreceptor”) is exposed to light to form an electrostatic latent image, and then toner is supplied to develop the electrostatic latent image, and the resulting image is transferred onto paper. After transfer, a cleaning blade is abutted on the surface of the photoreceptor to remove the toner remaining on the photoreceptor. Long-term maintenance of high cleanability of the photoreceptor leads to high reliability and durability of the image forming apparatus.
For example, a photoreceptor is known which has a protective layer provided on the surface thereof to prevent the wear of the surface caused by contact with a cleaning means such as a blade to maintain cleanability for the long term (see, for example, JP 2008-046198 A).
Further, a protective layer particularly excellent in wear resistance is known which contains metal oxide fine particles whose surface has been modified with a surface modifier having a reactive organic group in a cross-linkable cured resin obtained by curing a polymerizable compound (see, for example, JP 2013-257504 A).
Although such a protective layer has excellent wear resistance and can prolong the lifetime of a photoreceptor, a discharge product or paper dust is likely to accumulate on the protective layer so that surface resistance is reduced. This may cause so-called image deletion.
At present, a known effective means for preventing image deletion is to reduce the film strength of the surface of a photoreceptor so that the surface of the photoreceptor can be scraped off by a cleaning means, such as a blade, during use. However, if the film strength of the surface of the photoreceptor is reduced, toner fine particles or the like are pressed against the surface of the photoreceptor drum when slipping through the blade so that the toner fine particles are likely to firmly adhere to the surface of the photoreceptor drum. Further, areas where the toner fine particles are firmly adhered act as cores to block exposure light for forming a latent image, and as a result, there is a case where white spots, that is, so-called raindrop-like spots appear in an image.
Even when the hardness of the blade is increased to prevent the formation of cores that cause raindrop-like spots, scratches (surface irregularities) are formed on the surface of the photoreceptor by such a hard blade, which makes the contact between the blade and the surface of the photoreceptor poor. As a result, there is a case where slipping-through of toner occurs.
For this reason, there has been a demand for a photoreceptor that can maintain cleanability for the long term and can prevent the occurrence of image deletion, raindrop-like spots, and slipping-through of toner.